This invention relates to power transmissions and, more particularly, to multi-speed power transmissions employing planetary gearsets.
Planetary gearsets for automatic shifting power transmissions have been used in passenger vehicles and trucks for many years. The transmissions in the automatic phase progressed from two-speed transmissions to six-speed transmissions, which are currently used in some present day automobiles.
These inventions often incorporate a plurality of planetary gearsets, which are controlled by a number of torque-transmitting mechanisms known as clutches and brakes. The clutches and brakes are selectively engaged to establish the speed ratios desired through the planetary gearsets. Many of the proposed five- and six-speed planetary transmissions for use in today""s vehicles incorporate three planetary gearsets to provide those forward speed ratios. It has also been proposed to provide seven forward speed ratios in planetary transmissions, and in some instances, more than seven speeds.
It is an object of the present invention to provide an improved power transmission providing seven forward speed ratios and one reverse speed ratio.
In one aspect of the present invention, the transmission incorporates three simple planetary gearsets each having a sun gear member, a ring gear member, and a planet carrier assembly member.
In another aspect of the present invention, six torque-transmitting mechanisms are incorporated to establish seven forward speed ratios and one reverse speed ratio in the planetary gearsets.
In still another aspect of the present invention, one of the torque-transmitting mechanisms has placed in parallel therewith a one-way torque-transmitting device.
In yet still another aspect of the present invention, each of the planetary gearsets has one member connected to another of the planetary gearsets.
In a further aspect of the present invention, a member of one of the planetary gearsets is continuously connected to a transmission input shaft, which is continuously driven by an engine and input device such as a torque converter.